A variable valve timing control device disclosed in JP2016-180318A (hereinafter referred to as Patent reference 1) includes an electromagnetic valve controlling a relative rotation phase of an inner rotor and an outer rotor and a lock mechanism. The variable valve timing control device disclosed in Patent reference 1 learns a boundary between a phase control region and a lock region of an operation region of a spool of the electromagnetic valve, and performs a control based on the learning.
That is, the variable valve timing control device disclosed in Patent reference 1 includes a sensor portion detecting the relative rotation phase, and in a case of learning the boundary between the phase control region and the lock region, changes electric current supplied to an electromagnetic solenoid and memorizes an electric current value as a boundary electric current value in a case where the relative rotation phase is changed during the process of the change of the electric current supplied to the electromagnetic solenoid (at a time point when the lock mechanism is shifted in a lock state).
According to the variable valve timing control device disclosed in Patent reference 1, the electromagnetic valve is configured such that the spool is housed in a main body of the variable valve timing control device and the electromagnetic solenoid operating the spool is arranged outside of the main body of the variable valve timing control device. Considering a variance of the performance of the spool (an operating oil control portion including a spool) and the electromagnetic solenoid, the technology learning a boundary electric current as disclosed in Patent reference 1 is effective.
According to the learning disclosed in Patent reference 1, because the variable valve timing control device determines whether the lock mechanism is shifted to be locked by calculating a routine supplying a predetermined electric current to the electromagnetic solenoid in a state where the lock mechanism is unlocked, the same routine shall be repeated by changing of the electric current value supplied to the electromagnetic solenoid in a case where the lock mechanism is not determined to be shifted in the lock state.
Under the circumstances in which the variable valve timing control device repeats the same routine while learning, the learning takes time, and a user may feel uncomfortable by the unstable rotation of an engine in a case where, for example, the variable valve timing control device learns in a state where the engine (internal combustion engine) of a vehicle is operated.
Because the learning requires man-hour per variable valve timing control device according to the learning disclosed in Patent reference 1, issues of time consumption and manufacturing cost increase may be generated.
A need thus exists for a variable valve timing control device which is not susceptible to the drawback mentioned above.